Coated roofing



May 15, 1951 Filed Aug. 7, 1943 5 Sheets-Sheet 1 INVENTOR$ ATTORNEYLS May 15, 1 5 e. A. FASOLD ETAL COATED ROOFING Filed Aug. 7, 1943 5 Sheets-Sheet 2 'n. .lD.

Znyz/ur/Wg ATTOR N EYS May 15, 1951 G. A. FASOLD ETAL COATED ROOFING Filed Aug. 7, 1943 5 Sheets-Sheet 3 ATTORNEYS M y 15, 1 5 G. A. FASOLD ETAL COATED ROOFING 5 Sheets-Sheet 4 Filed Aug. 7, 1943 ATTORNEYS G. A. EASOLD ET AL comm ROOFING Filed Aug. 7, 1943 May 15, 1951 Patented May 15, 1951 UNITED STATES PATENT OFFICE COATED ROOFING George Arthur Fasold, Mount Healthy, and Harold W. Greider, Wyoming, Ohio, assignors to The Philip Carey Manufacturing Company, a corporation of Ohio Application August 7, 1943, Serial No. 497,803

15 Claims.

position. Usually there is applied to the bituminous coating on the surface intended to be exposed to the weather a suitable granular material such as slate granules or more finely-divided mineral surfacing material such as talc or mica. Finely-divided materials such as mica flakes, talc, silica dust or the like may be made adherent to the non-weather exposed surface of the roofing to prevent sticking of adjacent layers of the roofing material in the package.

The term roofing is used herein in the broad sense as referring to waterand Weather-resistant coverings such as shingles (individual or strip shingles), roofing tiles, cap sheets, sidings, roof deck coverings made from such preformed materials, built-up roofings, and the like.

The bituminous roofings of the character aforesaid that have been manufactured and sold heretofore have relatively low fire-resistance. The most widely-accepted tests for determining the fire-resistant properties of roofing are those prescribed by Underwriters Laboratories, Inc, of Chicago, Illinois. According to the tests prescribed by Underwriters Laboratories, Inc., fireretardant roofings are placed in three classifications, depending upon their ability to pass the tests required for each classification; these classifications being class A, class B and class C. The class C rating is the lowest fire-retardant rating and serves to distinguish roofings having appreciable fire-retardant properties from roofings having little or no fire-retardant. properties such as untreated wood shingles which, of course, are readily ignited and tend to burn freely. So far as we are aware, prepared bituminous roofings of the type heretofore on the market made on an organic fiber felt base have not been able to attain, regardless of the thickness thereof or the number of thicknesses, a rating of Underwriters Laboratories, Inc. higher than a class C rating. The class A rating is the highest rating awarded by Underwriters Laboratories, Inc. and is reserved for such highly fire-retardant roofings as asbestos-cement shingles of the double-coverage type. Class B is an intermediate rating and is, for example, awarded to roofings such as single-coverage asbestos-cement shingles. A brief description of the class A, class B and class C fire-retardant tests of Underwriters Laboratories is contained in our pending applications for Roofing, Ser. No. 370,636, filed December 18, 1940 (Patent No. 2,326,723), and Ser. No. 399,024, filed June 20. 1941 (Patent No. 2,326,724).

It is a purpose of this invention to improve the fire resistance of roofings comprising a layer of thermoplastic material such as bituminous material. Thus, for example, we have found that a roofing material which comprises an organic fiber felt base and a bituminous waterproofing coating can be made according to this invention, at the cost of ordinary bituminous roofing material, that is so highly fire-retardant that a three-layer covering on a combustible roof deck will satisfactorily withstand exposure to the class A fire-retardant tests prescribed by Underwriters Laboratories, Inc. We have found. further that such roofing material embodying our invention, when applied so as to provide two layers, will satisfactorily pass the class B fireretardant tests prescribed by Underwriters Laboratories, Inc.

The importance of fire-resistant properties for roofing is self' evident. Certain roofings such as asbestos-cement shingle, tile and the like have high fire resistance but such roofings are very costly as compared with asphalt felt roofings, and for this reason asphalt-felt roofings are very extensively used on all kinds of structures notwithstanding the limited fire-protection that is afforded by this type of roofing. According to this invention, asphalt-felt roofings can be made without substantial increase in cost which are comparable in fire-retardant properties to relatively much more costly roofing constructions such as asbestos-cement, tile and the like.

Substantially all bituminous roofings comprise a strain-resisting base or foundation sheet such as roofing felt which is coated with a bituminous coating that provides waterproofing and weather resistance. This invention has to do with the coating material rather than the base sheet. While the base sheet might be made of ZlOI1-CO1Ilbustible material, the non-combustibility of the base sheet does not solve the problem if the bituminous coating itself burns or tends to flow so as to spread the flame. According to the present invention, the waterproofing coating is rendered highly fire-resistant so that, even when applied to a base sheet of combustible organic fibers, roofing can be made which has the high degree of fire resistance mentioned above.

In our aforesaid copending application, Ser. No. 370,636 (Patent No. 2,326,723), we have described and claimed bituminous roofing comprising a bituminous waterproofing composition that,

while highly fire resistant, possesses physical" properties such as pliability and resistance to flexure that correspond in a general way with bituminous roofings of similar character previously manufactured and sold. The bituminous coating composition of the roofing disclosed and claimed in our application Ser. No. 370,636 contains bitumen having a softening point above 160 F. and of the range 45% to 70% by weight of the coating composition. The coating composition also contains filler" material of the range to 55% by weight of the coating composition. and in the form of finely-divided solid waterinsoluble heat-resistant mineral material of special character that is. described, illustrated and defined in our application Ser. No. 370,636.

In our application Ser. No. 497,805, whichv was filed simultaneously with our present application and which has resulted in Patent No. 2,424,234, we have described and claimed certain bituminous compositions especially adapted for use as mopping asphalt in the construction of built-up roofing, high fire resistance being obtained by the use of finely-divided solid water-insoluble heat-resistant. mineral filler within the limits of formulation therein described, illustrated and defined.

According to the present invention, organic filler materials which are not necessarily heat resistant are availed of to increase the fire resistance of the bituminous coating composition of bituminous roofings.

The surprising character of improvement of the present invention may be illustrated in the following way; If, for example, a conventional asphalt filler such as limestone dust or slate flour is mixed with the bitumen and the resulting bituminous coating composition is used as the coating for roofing, little, if any, improvement in fire resistance is attained not only when such filler is employed in amounts such as 25% to 40% by weight of the bituminous composition as has been proposed heretofore, but also when a larger proportion of such filler is employed, e. g., in amounts up to about 55% by weight of the composition. It is also the case that, if one attempts to incorporate an organic material such as cotton fibers, sawdust or the like in a bituminous composition as a filler within the limit as to quantity that can be incorporated while still aifording a mass that is spreadable in a heat plasticized condition, the resulting bituminous composition is devoid of effective fireresistance due to the combustibility of uch filler. However, by combining an ineffective filler such as slateflour or limestone dust with an organic filler such as any of those just mentioned which per se is likewise ineffective, one can, if the total filler is within thecritical zoneto be described hereinbelow, and if the amount ofheat-resistant mineral filler is sufiicient, obtain a highly fire-resistant bituminous coating composition. Moreover, this amazing result can be obtained even though the mineral filler is present in a relatively small amount such as to that is wholly ineffective in the absence of the additional 60m" bustible organic filler material.

By way of further illustration, a bituminous coating composition which contains mineral filler that, for example, consists of a mixture of asbestos dust and slate flour and that does not impart substantially improved fire resistance to the roofing, can be made highly fire-resistant by incorporating in the bituminous composition a combustible material such as finely-divided bituminous coal. This is most surprising ince a material such as bituminous coal is commonly used for fuel and one would not expect that the inclusion of bituminous coal would greatly increase the fire resistance of the bituminous coating composition of a bituminous roofing.

Ordinary coating compositions such as those that have been used for the weather-resistant waterproofing coating of bituminous roofings have little resistance to fire, even when, as aforesaid, the coating contains a mineral filler such as limestone dust or slate flour in amounts such as those previously employed. Such bituminous compositions when used as the waterproofing layer for an organic fiber felt tend to burn and become consumed when exposed to flame and to flow down an inclined roof deck, leaving the underlying fibrous sheet exposed to the destructive action of the heat of the flame so that the roofing as a whole burns through quite readily.

We have found that there is a critical point below which a filler material exercises very little effect in increasing the fire-resistance of a roof ing. At the critical point, however, slight further additions of filler exercise a very pronounced effect upon the stability of the bituminous composition. When the critical point is reached, the filler in the composition assumes the condition of a stable skeletal mat that holds the bitumen in place so that, even though the bitumen is rendered highly liquid by the heat of a flame, the bitumen is held in place by the skeletal mat. The bitumen when thus held in place carbonizes to form a cementitious binder that causes the mat of filler to become bonded into a continuous coherent protective layer that is prevented from becoming displayed by the carbonized residue of the bitumen- It is thus seen that, when the filler is present in the'critical amount, the resultant high fire resistance is due to a combination of factors which. area function both of the. filler and of the bitumen. Furthermore, during carbonization of the protective mat, pores. form therein which convert the mat-like residue into a heat insulating layer of very high heat insulating efiicie ncy.

The critical point at which a filler material forms a skeletal mat within a bituminous composition, when the bituminous composition is exposed to flame temperature, is a function of what we have found to be a measurable characteristic property that we have called the flow resistance property of the filler. This property is a property which, while an entirely different type of phenomenon, may be likened to the property of a substance in raising or lowering the boiling point of a liquid in which it is dissolved. As will be de- 7 scribed in detailhereinbelow, we have devised a th case o s a e fl u a d is about to by weight in the case of limestone dust. Certain filler materials of the planar-extended particle type such as fibrous material, e. g., asbestos fiber, or thin plates, e. g., mica, are more effective, but, as will be pointed out below, the effectiveness of different screen gradings of such materials differs considerably and it becomes necessary to select suitable screen gradings in order to achieve a high degree of flow resistance effectiveness.

The point at which high flow resistance is achieved is quite sharp, for below the critical point the flow resistance coefiicient remains low but suddenly increases when the critical point is reached. This critical point closely approaches the point at which the plasticity or consistency of the composition becomes excessive for satisfactory workability, Hereinbelow we have described a test for ascertaining the plasticity of a bitumious composition at 400 F. The suitable compositions for attaining high fire resistance according to this invention are found in a narrow zone defined by the requirement for high flow resistance and by the requirement that the bituminous composition not exceed the permitted maximum plasticity value at 400 F. The flow resistance coefficient and plasticity value are different properties, each of which is affected by the filler, but these properties are not complementary, for in some cases excessive plasticity at 400 F. results, even though high flow resistance is not attained.

According to the present invention, organic filler material is utilized for its effect in producing a bituminous composition within the zone which is limited, on the one hand, by the minimum fiow resistance coefiicient and, on the other hand, by the maximum plasticity value of the bituminous composition, Heat-resistant mineral filler preferably is relied upon to afford a noncombustible matrix for the skeletal mat, but the heat-resistant mineral filler need not in and of itself be utilized in the critical amount that affords a high flow resistance coefiicient, for the organic filler serves a temporary function of attaining the high flow resistance coefiicient. Thus the organic filler upon exposure of the bituminous composition of this invention to flame co-operates with the heat-resistant mineral filler in forming a stable skeletal mat and, upon continued exposure of the bituminous composition, becomes charred along with the bitumen, and, if consumed, leaves voids within the residual mat-like protective layer that augment its heat insulating effectiveness rather than otherwise.

In order to afford a better understanding of this-invention, it will be described for purposes of exemplification in connection with a typical embodiment, The roofing material of this embodiment is composed of strain-resisting roofing felt, a top weather surface coating of special bituminous coating composition, a surface layer of mineral granules partially embedded in the surface coating, a thinner layer of the special coating composition on the back of the felt base sheet, and finely-divided dusting material adherent to the back layer of the special bituminous coating composition.

In the exemplary embodiment, the base or foundation sheet is ordinary roofing felt made of vegetable and animal fibers, e. g., a roofing felt made from organic fiber stock weighing about 6 pounds per 100 square feet. is impregnated with a suitable impregnating material, e. g., a conventional bituminous roof- The felt ing saturant having a softening point of about F. to about F. The base sheet as thus composed has little fire resistance and, when exposed to fire, is consumed quite readily.

A typical example of the special coating composition may be made as follows: The bitumen used in the coating is preferably a residual asphalt flux from the refining of Mid-Continent petroleum which has been oxidized as by air blowing until it has a softening point of about 200 to 210 F. and constitutes about 45% by weight of the composition. With the asphalt there is admixed and uniformly distributed slate flour which constitutes about 47% by weight of the bituminous composition and cotton. fiber which constitutes about 8% by weight of the bituminous composition. The cotton fiber is fiber which passes a 6 mesh standard testing sieve and may, for example, be distributed about equally among the screen gradings from the grading just passing a 5 mesh testing sieve down to that passing a 200 mesh testing sieve. Such very fine cotton is of a dust-like character and heretofore has been regarded as a waste product of little commercial value.

In preparing the special coating composition, the asphalt is heated to a heat-liquefied condition and the cotton fiber and slate flour are thoroughly mixed therewith. The mixing preferably is carried out at a temperature of about 100 F. to 450 F. It is important that the bitumen and finely-divided filler be thoroughly mixed together so that the filler becomes intimately commingled and distributed uniformly throughout the mass and the composition should be applied to the felt base sheet While in a thoroughly mixed condition so that the filler occurs uniformly in the coating both as to amount and distribution and so that the resulting layer is substantially uniform in consistency and in thickness. In the typical embodiment herein described, the coating is applied to the felt base sheet at the rate of about 45 pounds per 100 square feet. Before the coating cools to atmospheric temperatures, a conventional surfacing material such as slate granules can be applied to the surface for weather exposure and these granules are partially embedded in the coating composition. The granular surfacing material is preferably non-combustible and, while employed, is not relied upon to impart fire resistance to the roofing. On the opposite side of the roofing material, there may be applied a thin coating of bituminous coating material, e. g., an asphalt having a softening point of about 200 to 240 F., so as to weigh about 5 pounds per 100 square feet, and finely-divided dusting or anti-stick material such as talc or mica dust or similar material may be applied and partially embedded in the back coating. Preferably, for maximum fire resistance, the back coating should be special coating composition embodying our invention.

The roofing thus prepared may be packaged in'sheet form, or, alternatively, may be cut into sections suitable for shingles or tile-like units. The roofing weighs about '95 pounds per 100 square feet. of this weight, about 30% by weight is in the form of mineral granules adherent to one side and finely-divided dusting material adhered to the other side, the balance of the roofing being felt, the bituminous impregnating material and the bituminous coating material.

The special bituminous coating composition may advantageously be mixed and applied in the manner mentioned in our said application Ser. No. 370,636 (Patent No. 2,326,723). As stated in said application, the coating composition may, if desired in order to increase the resistance of the applied coating to blistering, be" applied using the method and apparatus of our Patents Nos. 2,105,531 and 2,159,587, but this isnot essential.

The roofing material above described can be made up into suitable preferred roofing materials and. into suitable roofing structures, description of typical roofing structures being facilitated by reference to the accompanying drawings, wherein:

Fig. 1 is a plan view of a prepared roofing embodying this invention in the form of an individual shingle of simple rectangular shape;

Fig. 2 is a plan view of prepared roofing embodying our invention in the form of an individual shingle of a preferred shape;

Fig. 3 is a plan View of prepared roofing embodying our invention in the form of a shingle strip;

Fig. 4 is a fragmentary cross sectional view on an enlarged scale of prepared roofing embodying our invention;

Fig. 5 is a sectional elevation of an inclined shingle roof embodying our invention without showing the component layers of individual shingles;

Fig. 6 is an enlarged sectional elevational view of a portion of theroof covering shown in Fig. 5, as installed;

Fig. '7 is similar to Fig. 6 except that the roofing is illustrated as it appears after exposure to flame temperature;

Fig. 8 is a plan view of one form of prepared sheet roofing embodying our invention adapted to be installed in roll form;

Fig. 9 is a sectional elevation of a portion of an inclined deck with the roofing material of Fig. 8 installed thereon, the roofing material being shown with: exaggerated thickness for clarity;

' Fig. 10 is a side elevation partly in section of a testing device for testing the flow resistance of filler material as incorporated in a bituminous composition;

Fig. 11 is a plan view partly in section of the testing device;

Fig. 12 is a front elevation of the test panel assembly;

Fig. 13 is a side elevation of the test panel assembly;

Fig. 14; is a plan view'of the test panel assembly with parts thereof broken away;

Fig. 15 is a perspective view of the frame and guard plate used in the test panel assembly;

Fig. 16 is a longitudinal'sectional detail View on an enlarged scale of the orifice in the gas line leading to the burner of the testing device;

Fig. '17 is an end elevationof the Wagner- Bowen plasticimeter testing device;

Fig. "18 is a plan view of the plasticimeter;

Fig. 19 is a front elevation partly in section of the plasticimeter;

Fig. 20 is a side detail elevation of the drag tool and drag tool support of the plasticimeter;

Fig. 21A, Fig. 21B, and Fig. 210 are views of the f smoothing blade of the plasticimeter taken respectively in elevation normal to the line A--A of Fig. 18, from the bottom, and in elevation from the back in the direction of the line A-A of Fig.

Fig. 22A, Fig. 223, and Fig. 22C are views of 8 the mixing blade of the plasticimeter taken respectively in elevation normal to the line BB of Fig. 18, from the'bottom, and in elevation from the back in the direction of the line BB of Fig. 18.

The prepared roofing material may be cut into individual shingles l0 shown in Fig; 1. Preferably the roofing material is cut into individual shingles l0 having the shape shown in Fig. 2 or into strip shingles of the type shown in Fig. 3. Of course, shingles or the like of other shapes may be used in the practice of this invention. In cross section the prepared roofing material appears as in Fig. 4 and comprises a base or foundation sheet 13 of bitumen impregnated roofing felt. Overlying this roofing felt is a coating M of special coating composition having adherent to the surface thereof and partially embedded therein the slate granules l2. Adherent to the back of the roofing material is a layer 15 of the special bituminous coating material in which is embedded finely-divided dusting material 48. Ordinarily some bituminous coating material and dusting material are employed on the back of the roofing material, but these materials are not essential and are sometimes omitted particularly when the roofing material is to be used in built-up roofing.

In Fig. 5 is shown a typical roofing structure in place on a roof deck comprising boards l6 which serve as a support for the shingles, e. g. strip shingles H or individual shingles ID. The individual shingles may be 16 inches long over-all and laid with a 5 inch exposure, thereby affording triple coverage over all parts of the roof deck except for a portion of the spaces between adjacent shingles in each course. The component parts of the individual shingles appear in detail in the enlarged fragmentary view shown in Fig. 6.

In the installation of a fire-resistant roof covering, the employment of strip shingles of the type shown in Fig. 3 is preferred since the recesses or slots 23 only extend partially into the body of the shingle and since the notches 24 provide recesses of similar depth between abutting pieces of strip shingle, thereby preventing penetration of fiame into the body of the roof covering. Individual shingles Iii provided with a notch'25 are preferred forsimilar reasons.

The preformed roofing can of'course be laid with a greater proportion thereof exposed and so that the roof covering will be composed of two layers instead of three. Such a roofing is illustrated in Figs. 8 and 9. In Fig. 9 the roofing material is shown as installed on a roof deck with the thickness of the courses exaggerated for clarity. The preformed roofing material consists of a foundation sheet I8 of bituminized roofing material, coated over a part of its width with a coated with the special coating l9 and covered with the mineral granules 28, e. g., slate granules.

- This type of roofing may be laid on boards 2| of a roof deck using suitable securing means such as nails 26, the slate covered portion being exposed and the balance underlying an adjoining sheet as shown in Fig. 9. Where the preformed 'sheets overlap, they are caused to adhere to each other by' a bituminous adhesive material 22 which, preferably, is of the high fire resistance of the special coating compositions of our invention.

Instead of burning and flowing as is the case when an ordinary bituminous coating composition is exposed to fire such as that caused by a burning brand resting on the roofing, the special fire-resistant bituminous composition of this invention behaves very differently. The behavior of the roofing material as applied in three layers to a roof deck, e. g., as shown in Figs. and 6, is indicated roughly in Fig. '7. During exposure to fire, the special bituminous composition, instead of burning and running, remains in place due to the stabilizing action of the filler materials contained in the bituminous composition. As aforesaid, the slate flour by itself has little or no stabilizing action, but we have found that, when such filler material is combined with the cotton fiber of the character aforesaid, the bituminous composition remains stable upon exposure to the flame. The cotton fiber by itself does not have this effect, for, in order to effect the stabilizing action, the slate flour is also necessary in order to provide the proper ratio of fiber to asphalt in the composition whereby the high flow resistance coefiicient is obtained. During continued exposure to fire, the cotton fiber may be carbonized or entirely consumed, but this occurs as the bitumen becomes carbonized to a coherent cementitious material that holds the matrix of slate flour in place as a protective layer. Small bubbles 21 form in the composition as well as minute voids where the cotton fiber hasbecome consumed, and, as aforesaid, the resulting porosity of the mat-like residue greatly augments its effectiveness as a heat insulation.

In the roof covering as a whole as illustrated in Fig. 7, the upper layer of special bituminous composition has become expanded somewhat and has become somewhat irregular, but the coherent porous mat-like mass has remained and acts as a protective barrier against the flame. The uppermost layer [3 of felt may be carbonized and to a considerable degree may have disappeared leaving air pockets 28 together with some residual carbonized material. The intermediate layer 54 of special bituminous composition is also expanded, but remains in place as a protective heat insulating layer. The intermediate layer of felt is charred, but is better preserved than the uppermost layer of felt. The bottom layer of the special bituminous composition is less severely carbonized than the upper layerand likewise is considerably expanded. The bottom layer of felt is fairly well preserved and the underlying board It, if charred at all, has not become ignited. The backing layers [5, when composed of the special bituminous composition, likewise augment the heat insulating eifect of the roof deck covering, but it is not essential that these layers [5 be composed of the special bituminous composition of this invention. During exposure to fire such as a burning brand, the uppermost layer l4 may become red hot, but the heat insulation effectiveness of the carbonized residues of the layer I 4 is so great that the boards I6 may not even become scorched.

When the special bituminous composition of this invention is exposed to flame, the effect of the flame is confined to the area immediately beneath and closely adjacent to the area of direct exposure to flame and, when the flame becomes extinguished, all charring of the roofing soon ceases and the roofing cools down.

According to this invention, one can readily prepare roofing which, when applied triple coverage, e. g., as shown in Figs. 5 and 6, will pass the class A fire-retardant tests of Underwriters Laboratories, Inc. Moreover, such roofing, when installed double coverage, e. g., as shown in Figs. 8 and 9, can be made according to this invention so as to pass the class B fireretardant tests of Underwriters Laboratories, Inc. This high fire resistance rating can be attained notwithstanding that the roofing is prepared utilizing conventional roofing felt of organic fiber impregnated with a bituminous saturant. We do not know of any commercially prepared bituminous roofing made on a felt base of organic fibers which, irrespective of the number of layers or plies that are applied to the roof deck, will pass the class A fire-retardant tests; or even the class B fire-retardant tests, prescribed by Underwriters Laboratories, Inc.

In the above-described typical example of the practice of this invention, the combustible cotton fiber which in and of itself is Wholly ineffective, is combined with slate fiour, which is ineffective due to its lack of stabilizing action, to form a highly efiective filler mixture that has a high fiow resistance coefiicient and provides a bituminous composition within the limited range wherein high fire resistance is attained.

In order to accurately determine the flow-resistance coefiicient and thereby enable us to precisely define the highly fire-resistant roofings of this invention, We have devised a test whereby the flow-resistance coefficient of a particular filler or filler mixture in a bituminous composition under conditions of exposure to fire may be measured. The test consists in directing a fiame against an inclined specimen of roofing that carries a coating consisting of the bitumen and the filler or filler mixture to be tested, under precisely-controlled conditions determined by the construction and operation of the testing apparatus. The following is a description of the controlled conditions of the test, reference being made to Figs. 10 to 16 of the drawings.

Samples carrying the bituminous composition containing the filler or filler mixture to be tested are made by applying the bituminous coating composition to the base sheet material so that the coating weighs 30 pounds plus or minus 2 pounds per square feet.

The test is made in a wind tunnel 50 having a fan 5| at one end and a stack 52 at the other end. The tunnel is made of inch thick asbestos-cement lumber and has two windows 53 and 54 therein which can be opened and closed by any suitable means (not shown).

Within the tunnel are the burner and testing deck which are located between two shields 55 and 55 of the asbestos-cement lumber spaced 12% inches apart, and which are rigidly mounted on the asbestos-cement slab 56. The inclined test deck is indicated generally by the reference character 5! and comprises a lower frame-like member 58 having 4 inch pegs 59 projecting from the face adjacent the upper and lower margins. Between the pegs, strips iiil of asbestoscement boards, 1% x 12 x inches are placed. One ply 12 x 12 inches of the prepared. coated sample 13 to be tested is placed on the asbestoscement boards fill followed by an L-shaped guard plate 6! which coversthe bottom edge of the sample. The assembly is held down by an iron frame 62 and held in place by thumb screws 63.

After the test deck has been assembled, it is portion of the deck exposed to the flame.

agsscgom placed: on: the inclined support '64" whichhas. an opening. in the" back underneath the strips as and which has side flanges 55 to protect each side of the" test panel. The support 6'4 comprises a 'baiiie tuto -prevent the flame licking around behind the' test deck. The support, which is made of iron, is mounted on theasbestos-cement slab 56 whi'ch measures 12 x 40 x1 inches. The parts fon carrying the'test deck are also made of iron. ironbar 61, 12 x l xinches is' place across the ..top edgeof the deck to protect the sample a'tthis point. 7

'In front ofthe testdeckis the burner 68 comprising an iron -pipe having aninside diameter of .472 inch and anout'side diameter of .675 inch with 17holes'0.078 inch in diameter and /2 inch apart disposed at an angle that is parallel with theplane of the test deck. The burner is provided-with an inlet line 69 controlledby ashutoff valve 10'. Inthe line 69 is an orifice l5, inch in diameter, that is located in the housing connections-ll. Between the valve 10 and the orifice is-a manometer 12-. By thisa-rrangement, a supplyof gas under constant pressure can be obtained; thereby obtaining a steady flame of constant intensity during the test.

At the base of the test deck and between the burner and the deck holder is placed a pan 14, x l x 10 inches-, which collects any bitum'inouscoating materialthat flows from the sample during the exposure to the flame. This pan is provided with a removable cover 15.

The dimensions of the different parts of the testing apparatus'shown in the drawings as used by us are as follows;

a-24 inches -8 inches 6 3:8 inches -2 inches b"6 inches q% inch cl8 inches r1 inch (2-72 inches s-12 inches el6 inches t7 inches 1 -10 inches ul0 inches yl 2% inches i)-12 inches h-38 inches w12 inches i-Gi inches x'1 inch 7' 3 2 inches y12 inches k2f1 iI1Qh-)S y-l inch Z24 inches z-6 inches m -fl 0 inches act-l2 inches n27 inches bb1 inch Incarrying out the test, the apparatus is first assembled and the burner is lighted so as toprovide a pilot flame that is about inch in length when the fan is operating. The windows 53 and 54 are then closed and the room in which the apparatusis placed is arranged so that there will be relatively constant conditions during the test. The temperature and relative humidity of the room should be approximately 80 F. and 40%, respectively. The fan should generate a wind velocity of about 150-155 ft. per minute at the The valve H! is then opened until a flame about 8 to 9 inches long is produced having a temperature of about 1325-1370 F. When the valve 10 is opened to produce such flame, a timing device is started. After the sample has been exposed to the flame for a period of five minutes, the flame is turned oil and simultaneously the cover is placed over the top of pan [4 so as to prevent any further bituminous composition that may flow down the test deck from collecting in the pan. Before the commencement of the test, the pan M is carefully weighed and at the conclusion of 1 2 the testis againweighed;thedifferene-in weight being the number of grams of bituminous coating material that has flowed into the pan. Before making the test, the weight of the bituminous coating on" the test sample is determined by weighingthe base sheetmaterial before the bituminuous coating is applied thereto and weighing the complete sample, the difference being the weight of the coating.

The coefiicient of flow resistance is' computed, according to following expression.

weight in grams ofcoatingcollected in pan 100 total weight in grams of coating prior to test 7 For example, if the weight of the bituminous: coating on the sample was 1000 grams prior to testing" and 50 grams ofthe coating were collected in the pan during tl'ie" test, the 'coeflioient; ofl'fiow resistance would be lf no coating composition flows into the pan,

then th'e'flow resistance coefiicient is 100 which is. the maximum, attainable.

The flow resistance coefficient is primarily a. function of the filler contained in the bituminouscomposition since the greatly-=increasedflow resistance of the coating, if attained, is due to presence of the filler in an amount that equals or ex ceeds the critical amount for the filler under-- going test. It may be mentioned, however, that: the, amount of a given filler that is critical will usually vary somewhat depending upon the bitumen that is used in the bituminous composition. Thus the critical amount of filler for a so-called cracked asphalt, namely, oxidized asphaltic: cracking still residue, is usually somewhat less than for a straight run asphalt residue.

Another factor that influences the fiow resistance' c'oefiic'ient somewhat is the character of the surface to which the bituminous coating com-- position is applied. In the manufacture of roofing material; a typical asphalt saturated felt base sheet weighs about 30 lb. per 100 square feet and is saturated to the extent of about 175% by weight with asphalt having a softening point of about F., so for most purposes an asphalt saturated felt such as this may be used in making the test. However, for bituminous compositions which have incorporated the critical amount of filler to render the composition highly flow-resistant, the asphalt in an asphalt saturated base sheet exerts an efiect as a lubricant at the interface between the base sheet and the coating composition which tends, depending upon the amount of asphalt in the base sheet, to lower somewhat the flow resistance coefiicient as determined by the test. This effect can be counteracted by indenting or otherwise causing the surface of the felt base sheet to be rougher than normal. By using. adry or unsaturated felt base sheet, especially base sheet material having relatively coarse fibers, the flow resistance coefficient of the bitmuinous composition per seris attained without being influenced by any effect resistant bitmuinous coating composition can'be formulated so that the flow resistance coeflicient will be as high as 100. However, greatly improved fire resistance is obtained according to the invention when the flow resistance coeflicient of the filler in the coating of the roofing in question is 75 or greater, although it is preferable to formulate the bituminous coating compositions so that the flow resistance coeificient of the filler in the bituminous coating composition is 90 or above.

The practice of this invention may be illustrated in connection with another type of highly fire-resistant bituminous composition which contains asphalt, fibrous mineral filler, a non-fibrous mineral filler and a non-fibrous organic filler such as bituminous coal. In the following example as well as elsewhere herein, the percentages given are percentages by weight. The screen grading of asbestos passing a 14 mesh standard testing sieve and retained on a 20 mesh testing sieve is indicated as (-14-1-20) and the other screen gradings are indicated similarly both in the following example and elsewhere herein.

Percent Asphalt (softening point 220 F.) 4 Slate fiour 6 Powdered bituminous coal 20 Asbestos dust gradings:

-l4+20 1.5 20+28 2.0 -28+35 2.0 35+48 2.5 -48+65 3.0 65+100 2.0 l+150 3.0 -150+200 3.0 -20o 10.0

Total asbestos dust 29 A bituminous composition such as that described in the foregoing example has high fire resistance. If, in the above composition the 20% by weight of powdered bituminous coal is omitted and the bitumen content is correspondingly increased to 65% by weight, the composition is not particularly effective in providing fire resistance due to the fact that the screen gradings of asbestos fiber in the amount used, coupled with the slate flour, do not provide an adequately high fiow resistance coefiicient. However, the presence of the bituminous coal increases the ratio of the asbestos fiber to the asphalt so that a composition of high fiow resistance coefficient is attained. The result is that, even though the powdered bituminous coal is combustible, it imparts initial stability to the bituminous composition when the bituminous composition is exposed to flame temperature so that the bitmuinous composition carbonizes while remaining in lplace, the heat-resistant mineral filler providing a non-combustible matrix for the residual protective skeletal mat of filler.

From the foregoing examples of the practice of this invention, it is apparent that, according to this invention, organic filler material, whether fibrous or non-fibrous, is utilized to increase the stability of the waterproofing bitumenin the bituminous coating. In this way, a combustible material, even one such as coal that burns readily, can be availed of to greatly increase the fire resistance of roofings when utilized in bituminous compositions formulated within the aforesaid limits as to fiow resistance coefficient and plasticity value. If, on the other hand, such'combustible organic filler is used in a bituminous composition that does not come within such critical limits, it promotes combustibility and the advantages of this invention are not attained.

The highly fire-resistant bituminous compositions of this invention are, generally speaking, bituminous compositions wherein the total filler material is of the range 35% to 80% by weight of the bituminous composition, the waterproofing bitumen being of the range 20% to 65% by Weight of the coating composition. While the: general range of filler content is seen to be subject to considerable variation, it does not follow' that a given filler or filler mixture will be effec tive within this broad range. In fact, in the caseof most fillers and filler mixtures, the critical, range within which they can be used to achieve the high fire resistant bituminous compositions of this invention is confined between limits that are imposed by the minimum flow resistance coefficient and the maximum plasticity value and that permit variations of filler content of only about 5% to 15% by weight. However, the critical points for the different fillers and for filler mixtures will diifer quite widely and may be,for example, around 35% by weight of the coating composition or may be around 75% by weight of the coating composition, depending upon the particular filler or filler mixture that is employed.

In preferred embodiments of this invention the filler material is provided with a non-combustible matrix for the skeletal mat of filler by utilizing in the bituminous composition finely-divided solid water-insoluble heat-resistant mineral filler, either fibrous or non-fibrous. By heat-resistant any material is intended which is sufficiently heat resistant to retain structural integrity when subjected to flame temperature while incorporated in the roofing. In this connection, substances such as chrysotile asbestos, Canadian pic-- rolite, hydrated Portland cement, etc., are regarded as heat-resistant even though they contain water of constitution which may be driven off at temperatures below flame temperatures. The amount of heat-resistant mineral filler that it is desirable to employ in preferred embodimerits of this invention depends upon the percent by weight of waterproofing bitumen contained in the bituminous composition which in turn is a function of the percent by weight of the total filler. Thus in preferred embodiments of this invention the heat resistant mineral filler is employed in an amount such that the ratio of the percent by weight of the heat-resistant mineral filler to the percent by weight of bitumen in the bituminous composition is at least 1 to 3. It is even better in the practice of this invention that the ratio of the percent by weight of heatresistant mineral filler to the percent by weight of bitumen in the composition be at least 1 to 2. The amount of organic filler that is mixed with the heat-resistant mineral filler is subject to Wide variation. Thus the organic filler employed in' the fire resistant bituminous com-positions of this invention may be present in very small amount such as 2% to 3% by weight of the bituminous composition, yet, especially when such organic. filler is in the form of fiber of highly effective screen grading, the presence of such small amount of organic filler can be critical to the attainment of a highly fire-resistant bituminous composition- The term organic filler, as used herein, is intended to include those substances in finelydivided, solid particulate-form, within the size! l 7 range set forth, which are predominantly organic compounds of carbon, as distinguished from inorganic carbon compounds such as metallic carbonates. Organic fillers may be of vegetable or animal origin, i. e., produced by the life processes of plants and animals, or may have been derived from, vegetablev or animal matter by chemical and mechanical processes of nature, as exemplified by coal. Cotton, wood cellulose and cork are examples of organic fillers of vegetable origin. Wool and other animal hairs are organic fillers of animal origin.

Organic fillers also may be derived from vegetable and animal materials of. natural origin by chemical or mechanical. treating processes. Regenerated cellulose or cellulose acetate fibers areproduced from cotton or wood cellulose. Coke from coal and petroleum coke are other examples. Chemically refined. wood pulp, ground wood; and defiberated wood and other typical or ganic; fillers. Synthetic resins exemplify organic fillers produced by artificial processes rather than by natural processes.

Organic fillers may be either fibrous in structure, as cotton, Wool, hair and wood fiber, or may be non-fibrous, such-as coal, coke, petroleum coke, cork resins, etc.

In the formulation of fire-resistant bituminous compositions, it is preferable to utilize fibrous filler, or, more generally a filler of the planarextended particle type as part or all of the filler material, since such filler materials have the property of affording a high degree of flow resistance. The use of such filler materials is especially desirable when the total. filler content ofrthe bituminous composition is less than 55% by weight. As aforesaid, we have found that such fillerrmaterial's differ considerably in their effec tiveness. depending upon the screen grading of the filler material in question. This can be illustrated in connection with a mineral filler such as; asbestos. dust when employed in combination with a. filler such as slate fiour that has little effectiveness in. the stabilization of bituminous compositions. Thus, when the screen grading of asbestos dust is (28+35), a composition consisting of. substantially 23% by weight of this screen grading of asbestos dust, 17% by weight 'ofslate flour about 85% by weight of which is (20.0) and.60.% by weight of asphalt of softeningpoint of about 230 F. will have a fiow resist.- ance coelficient of about 75. Ifthe screen grading ofasbestos dust is (+.14), only about 6.5% by weight of asbestos dust (the balance of the composition being 33.5% of slate flour and 60% of asphalt) will achieve a flow resistance coeflicient of about 75. In view of these differ ences in effectiveness of the different screen gradings of a mineral fiber such as asbestos dust, we have, in order to indicate more definitely the amount'of mineral fiber of given screen gradings that is required to effect stabilization of a bituminous composition, assigned to the different screen gradings what we have called the screen factor for each of the difierent gradings. Thus if, the screen grading (-28+35) is taken as having a screen factor of unity, any screen grads ing that requires half the amount as compared with the screen grading (-28+35) will be twice as effective and will have a screen factor of 2. On the other hand,.a screen grading that requires twice the amount as compared with the screen-grading (28 +35) will only have half-the effectiveness; and willhave. ascreen grading of 0.5; In like manner, screen factors can be as signed to each of the other screen gradings.

The above-described test for measuring the flow resistance coefficient of a filler in a bituminous composition affords a convenient basis for setting up the screen factors of fibrous mineral fillers ona definite scale and, when the screen factor of a given screen fraction of a fibrous minera is referred to herein, the screen factor as determined in the following manner is intended. The test for determining the flow resistance co efi'icient is carried out using the test apparatus and procedure above described except thatin all cases the total filler is 55% by weight of the bituminous composition. The asphalt in all cases is air blown (oxidized) straight run asphalt hav' ing a softening point of about 230 F. Slate flour about by weight ofwhich passes a 200 mesh testing sieve is used in all cases, as the standard diluent filler, and the amount by weight of the particular screen grading of fibrous mineral to achieve a flow resistance coefficient of about '75 as ascertained by the average of a'pluralit'y of test runs, is determined. Each sample" is pre= pared using the impregnated organic fiber felt above specified, namely, conventional asphalt saturated organic fiber roofing felt weighing about 30pounds per square feet that has been impregnated to the extent of about 175% by weight with asphalt having. a softening point of about F. Asa standard, chrysotile asbestos ofthe grading (28 +35) is taken as having a screenfactor of unity and the factor for each of the other gradings is calculatedto this standard. By way of concerete example, it being the case that substantially 15% by weight of the bituminous composition, of chrysotile asbestos having the screen grading (28+35) (the total filler being 55% as aforesaid), is required to afford a flow. resistance coefficient of substantially 75, and it also being thecase that only about 3% by weight of the bituminous compositionsof chrysotile asbestos of the screen grading (6+8) (the total filler again being 55%), also affords a flow resistance coefficient of about 75', the screen factor of chrysotile asbestos fiber having the screen grading (-6+8) is seen to be 5.

By' way of further illustration, the screen factors of the different screen gradings of a typicaljchrysotile'asbestos. fiber on the basisabove mentioned are as follows:

Screen Screen Grad g Factor r a s-we s" moauscv zoco-aswovooc') It may-be noted that in the case ofthe-screen grading 2 00), a-flow resistance-coefiicient of '75, was not attained even when; the total filler (55% by weight) consisted-of this particular grading of asbestos-dust. However, since: this particular screen-grading (-200) is nevertheless somewhat effective when combined with the more effectiverscreen gradings, a screen factor of .2- hasbeenrassignedto this particular screen grading, Similarly, in the casesof any'otherfibrous i e a saa: ree er d na W h n m l yed to the-extent -of-- 55% by'weighty does not attain a flow resistancecoefficient of --'7 is to beregarded as having a-screenfactor of L21 The foregoing isseen-to afforda convenient Wayof knowing and definir-ig theflow resistance ef fectiveness of a fibrous fillersuch' as asbestos: Given the percentage ''byweight of-"eachof the screengradi-ngsof fiber "contained-in a bituminous composition, the -percentageby weight of each multipliedby the screen 'factor foreach gives what we term herein and in the-claims the-grading index for each of thescreen gradings; and,-

by adding the grading-indices for the several screen gradings together, the grading indexforthe totalmi-neral fiber isreadilydetermined: By way of illustration, the "grading index of the fibrous mineral filler componentofthe abovementioned typical embodiment .of'thisinvention containing asphalt, slate flo'urr and powdered bituminous coal is-asfollo'ws:

Percent by t Weight of Composition Screen 1 Factor 1 Screen Grading Grading Index g e es lg XXXXXXXXX Total grading indexforininer tfiber.

The mineral fiber filler tliat is preferred in the practice of this invention is asbestiform mineral l fiber, chrysotile asbestdsdust-beirig especiallyde sirable. Other asbestifo'rm mineral fibers-ofthe particle size 'mentionedmay likewise be emtributed therethrough. A convenient source of such material "is asbestos-cement roofing scrapj which usually contains about to by;

Weight of asbestos fiber and" about to80%' of hydrated Portland cement. Heretofore such scrap has been regarded as anunavoidable waste of no commercial value: However; by subjecting thescrap to a disintegratorsuch'as a-hammer mill, the resulting mass contains a multiplicity of short asbetos fibersto' which the hydrated Portland cement adheres as nodules and for this-reasonthis materialis-fib'rous and is to be included in "the term fibrous mineral;

Another material which is somewhat similar" to asbestos-cement in thatthe material" contains mineral" fibers together with seme non-fibrous material, is disintegrated -fiber-'bearing serpentine rock. Since disintegratedfiber bearing serpentine rock contains fibrous particles; such" disintegrated serpentine rock' is regarded asoneform of fibrous mineral whicfiis suitable for use i in practicing this inve'ntionQ However, depend ing upon the physicalstructu're' and fibrous mineral content of the"particular serpentine rock that i is used; the proportion of fiber contained pointed. out below, 'tl'iism'erely has the-effect of varying somewhat the screen ifac'tor's of the vari ous: screen gradings of the disintegrated serpen of-the screen grading (28 |-35) which has ascreen factor of unity. Moreover, disintegrated fiber-bearing serpentine rock is of such character that in order to liberate the fibrous material contained therein itshouldpass a 20 mesh testing sieve, and, When reference is made herein to disintegrated fiber-bearing serpentine rock, only thatserpentine rock which has been disintegrated so that it passes a 20 mesh testing sieve is intended, since individual particles of coarser gradings are not fibrous in character but granulardare not'fibrous mineral asthisterm isused herein) 1. and since such coarser gradings are in effective in *producing highlyyfire-resistant roof lngS."

Other-mineral fibers may likewise beemployed'; such -as mineral Wool andglass fibers. 'Ihetermminer-a1 l wool includes various products obe tained by attenuating into fibrous formxsuitable" therein is subject to some variation, but, as

fused materials such as rock or slag;

Of the fibrousfillers other than mineral fillers, there is a wide selection of animal, vegetable," and synthetic fibers; In addition to cotton, one may employ-wood fibers such as fine sawdust," or defiberated wood and paper and paperfibers: such as ground wood, sulphite, and kraft paper pulps; Finely-divided Wool'fiberisalso suitable but is much more costly. Synthetic fibers such as regenerated cellulose (rayon) and cellulose" acetate also maybe used.

In addition to fibrous fillers, another fillerthat is'similarto'fibrous"fillers in thatit is effective varyingdegrees depending upon the. screen grading or mixture of screen gradings thatis employed, is mica. Mica is characterized :by its 0ccurrencein-the formof small plates which are thin relative to their lateral extent. Mica and fibrous materials are characterizedby.tl 1e fact that at least one dimension is very small relative to another more-extended;dimension. Such materials are therefore. referred to generally herein as-planareextended filler materials, there.

by; indicating that the particles are in the form,

offibers or are 'in' the form of plates having an extendeddi'mension that is. confined essentiallytoonly one of the three dimensional. planes In,

the-case of 'aifiller "such as mica that existsinthe form of, plates, particles which are retained on a 14'mesh' testing-sieve are undesirable in the com:- position.

With regardito fibrousfillers .otherthan as-.

bestiform mineral fibers, it is not usually the case; thata particular screen. grading of, for example,

asbestos-cement, cotton, wood fiber, etc., will havethe samescreen factor as that of ,Ch-TYSQ? tile asbestos fiber. In fact, even ;as among. dif-r ferent typesof asb'estiform,.mineral fiber. there are some variations .in this. regard However, utilizing chrysotile asbestos= dust as. the stand-=- been described hereinabove. Byway of illustration," the screen"factor"ofdisintegrated asbestoscement roofingsscrap of the screen grading For defiberated wood' 28'4-35) is about? 3;? fib'ergthe same screen grading has a screen factor of about :"4 and fo'r cotton of the same screengrading the screen factoris about 6; However;

fibrous fillers; particularly in the case of wood tine 'rocki as calculatedto'chfysotile asbestosldust" fibers; cotton and "the like are subject to con- I siderablevariation, and for this reason the screen factor'and grading index has been calculated to chrysotile asbestos fiber, which is more uniform in its physical characteristics, as the standard. The foregoing with respect to the screen factors of other fibrous fillers also applies to the screen factors of mixtures of planar-extended fillers, calculated to chrysotile asbestos dust of the screen grading (-28-1-35) which has a screen factor of unity. r

. In ascertaining the grading index of a filler of the planar-extended particle type for use in a highly fire-resistant bituminous coating composition, the grading index required will vary with the amount of bitumen in the bituminous composition, the amount of bitumen being, of course, an inverse function'of the total filler. When the amount of waterproofing bitumen in the bituminous composition is about 45% by weight, the grading index of the planar-extended filler is desirably about 15, while for a total bitumen content of about 65% by weight of the bituminous composition the grading index that is desirable for obtaining a similar stabilization of the bitumen Will be about 31. More generally, in the practice of this invention it is desirable to employ filler of the planar-extended particle type having a gradingindex the ratio of which to the percent by weight of waterproofing bitumen in the bituminous composition is at least 1 to 3, and pref erably is at least 1 to 2. This is especially important in the case of bituminous coating'composition containing a total filler content of the range 35% to 55% by weight of the bituminous composition.

For a total filler content above 55% by weight of the bituminous composition, it is likewise advantageous to employ a finely-divided filler of the planar extended type, although the ratio of the grading index of such filler to the percent by Weight of bitumen in the bituminous composition can be somewhat less. Thus, in the case of total filler contents of the order of 55% to 65% by weight of the bituminous composition, the ratio of the grading index of the planar extended filler to the percent by weight of waterproofing bituously, at least 1 to 6 and preferably is at least 1 to 4. For filler contents of the order of 65% to 80% by weight of the bituminous composition, the ratio of the grading index of the planar extended filler to the waterproofing bitumen in the bituminous composition is at least 1 to 8 and preferably is at least 1 to 6.

When reference is made herein to screen factor and grading index of a filler of the planar-extended type, the reference is made to these values when determined as hereinabove de-. scribed. When, however, reference is made to flow resistance coeflicient of a filler or filler mixture, the fiow resistance coefficient, unless otherwise specified, is that of the filler or filler mixture in whatever amount it is present as commingled with the kind of asphalt employed in the bituminous composition, the bituminous composition being tested as applied to the base sheet of the commercial product.

In determining the screen fractions or grading of fibrous or other mineral fillers that are referred to herein, 8 inch diameter testing sieves of the W. S; Tyler Company sieve series, meeting A. S. T. M. Standard Ell-39 for Sieves for Testing Purposes have been used. A quantity of filler to be screened, ranging from 200 to 300 grams, is placed in the uppermost of a series of men in the bituminous composition is advantagetesting sieves and'subjected to suitable agitation as in a standard W. S. Tyler Company RoTap sieve shaking machine for a period of five minutes-in order to separate the original filler roughly into fractions retained in: the different testing sieves. This operation is repeated, if necessary, in order to obtain about to 200 grams of the desired screen fraction, which fraction is then individually rescreened for 15 minutes, using the R0 Tap screening machine or the equivalent in order to remove any fines contained therein. The resulting screen fraction is material that has passed the coarser screen and is retained on the finer screen.

When a filler of the planar-extended type is used, such filler shouldbe used in the finelydivided or dust-like form as distinguished from long cotton, wood or asbestos fibers. Fibrous fillers that are retained on a 6 mesh testing sieve are undesirable in the coating composition. It has been mentioned above that mica retained on a 14 mesh testing sieve in undesirable. Accordingly, and somewhat more generally, it is desirable that the filler material of the planar-extended type be confined substantially to that which passes a 6 mesh testing sieve and which does not have more than one dimension greater than about .046 inch, which is the width of the opening in a 14 mesh testing sieve. When a filler of the planar-extended type is used that is coarser than has been mentioned above; such filler ma-.

terial tends to forminto clumps or clots which render the bituminous composition non-spreadable to the uniformity that is required in a commercial product and also impair 'the fire resistance due to occurrence of zones of insufiicient protection and due to poor adhesion to the underlying base sheet upon exposure to fire. For this reason, it is highly desirable to limit the quantity of the coarser planar-extended filler to that which can be incorporated in a bituminous composition that, when heat plasticized, is spreadable to form a layer of uniform thickness and uniform consistency. In this connection, a slightly pebbled appearance of the surface is permissible provided the coating as a whole provides a good waterproof and weatherproof layer. It is usually desirable that less than 10% by weight of the total. content of the bituminous coating composition consist of a filler of the planar-extended type which is retained on a 14 mesh testing sieve, although in the case of mineral wool a substantially greater proportion of such coarse material can be incorporated in a spreadable composition. While the presence of any fiber retained one 6 mesh testing sieve is'regarded as undesirable and while the presence of any mica retained on a 14 mesh testing sieve is regarded as undesirable,

, anysmall quantity of such excessively coarse planar-extended filler that may be present while still retaining spreadability is to be regarded as having the same screen factor as that of the fraction (-6+8) in the case of fibrous materials and the fraction (14+20) in the case of mica.

-Usually, it i desirable that the ratio of the gradtion at which the filler or filler mixture in quesfire-resistant bituminous compositions according to this invention; .it'is' desirable that the plasticity;-

of thebituminous composition at--400=F. not'become. excessive. upon the amount of ordinary fillers which may be incorporated but also imposes a limit upon the I amount of fillermaterialsof the planar-extended type; particularly in the coarser gradingsythat may be incorporated.

The plasticity value a of ==the "bituminous come position has been determined by? us,,using a Wagner-Bowen 'mixingbowl plasticimeter-,- manufactured by: E. E. W.- Bowen,-Bethesda; Maryland; For testing bituminous compositions of the character mentionedherein; vwe have made certain modifications -in this :test apparatus.

wherein this type of apparatus is described in detail, we have shown in the ;drawi-ngs,-Fig, 17

to Fig. 220, the testing apparatus which we=haveemployed and a description of rthe appa-ratus and its operation follows. Whenreference is made herein or in the claimsto- Wagner-Bowen plas ticity value, the plasticity value as v=-deter-mined by this testis intended= The Wagner-Bowentplasticimeter consistsot a suitablebase I which comprisesin housing:

I43 suitable gearmeans (not: shown). for rotating the vertical shaft I0I-by-powersupplied from I themotor I02. Theshaft IOI carries -for. rotationat the upper end thereof, the horizontally.-

disposed disk-shapedsupport I03 to the top :of which is securedthe bowl .I04-bymeansof screws I05. By this arrangement, the bowl-I04- can be rotated by operation of: the {motor -I 02, andiany suitable means can be provided formaintaining the rotation-of thebowl at. apredetermined con-4 stant speedc Emanating. from the ,base. I00 are I arms I06 and I06- which carrycntheupperends thereof the crossbar I01. At. the upper end of each arm I and lflfi isa yoke -I08..which is :pivoted to.

lug: I09 and which is provided with a thumb screw III) in. threaded engagement therewith so that. by loosening-the .thumbscrew 1 I0, the yoke Illfican be swung outwardly, permitting .removal of the cross bar I01. At each end-of the cross bar I01 is a positioning .pin I H by which the position of thecross bar is determined.

The cross bar I01 carries the means determining the plasticity of material in thebowl' I04.

Carried .at the lower'end of shaft 1 I2 is the mixing blade I I3, the vertical position ofgwhich relative to the bowl I04 is adjustable by nuts 4- which secure the shaft II2 to the crossbar I01. Adjacent the-end of the mixing blade I I3 is'the thermometer II5 carried in a guard I I6 attached to bracket II 1 which in turn is securedatthe upper end tothe cross barI01. Carried by the lower end of the shaft I I Bisth'e smoothing blade I I9? The shaft I I8 and smoothing blade Sara A urged downwardly by the expansion-spring I between. the annular washer I22 and the sleeve IZI :in which the shaft H8 is :verticallyslidable.

The vertical position "of the smoothing blade I I9 1 isdetermined by the thumbscrew :I 23 which-rests against the upper end ofsleeve -I2I and which is.

in threaded engagement with the. upper end Of: the' shaft I I8. Alsorigidly secured to the 1- cross:

However, excessive addition-of filler- In view of this fact and further in viewof the fact I that we do not know of anyiava-ilablepublication qpan I31.

bar JI 01 is the) rod 1 24, the, lower end oflwhichcanbe adjusted so as ;to be a predetermined distance from the bottom of the bowl I04 by nuts I25.

At the center of the cross bar I01 is the bearing I28 for thevertical shaft I21 that is'mounte'd for rotation'therein at a given vertical position. Rigidly securedto the shaft I21 by means of the collar I28 is the arm I29 which carries'the small" cylindrical drag tool I30 at the lower end thereof.

end of which has a small amount of play for angular movement with the shaft I21 between opposed adjustable stop screws I32.

A horizontally-disposed stub shaft the arms I and I36 extending horizontally on opposite sides of the stub shaft I33. Pivotally secured at the end of the arm I35 is the weight pan I31 and pivotally securedat the end of arm I36' is the counterweight I38 which substantially,

counterbalances the weight pan about stublshaftv I33. Betweenthe end of arm I3I and theend of arm I34 is the tie rod I39. tie rod I39 has-aturned down portion I40 which slips through an'opening of corresponding size) in the end of arm I3I to provide pivotal movemcnt with'respect thereto. The other end of tie I rod I39 is in threaded'engagement with "ayoke member I4I which. is pivotally mounted withrespect to the upper endof arm-I3 I.' If desiredyiai fixed stop arnrIM' canbe provided forconven ience in rest-raining :movementofarm I34 when thetie rod I39'isdisengaged from arm I3I.- The contents ofathje bowl: I 04 can be heated as bythe gas burners-l42r In the operation of theplasticimeter, the-bowl I0 1 is rotated in-fa clookwise-direction, and; as

the bowlcontinues to operate, the mixing blade I I3 scrapes the heatedcontentsof the bowl away from the outside bottom portion thereof'and the thermometer II'5 records the temperature of :the contents of the bowl atthis point. The contents of the "mixing bowl are next carried under the smoothing blade I I9-1 which smooths thecontents of the bowl to a predeterminedlevel above the outer portion of' the bottom of the 'bOWlr The lower' endof the rod-I24serves as a-check to determine -whether-thesmoothing blade II 9 is.

smoothing-the contents of the mixing bowl to the desired level,- andyif it is not; the vertical position of the smoothing blade! lIlis adjusted by thumb screw I23. The heated contents of the: bowl at the' predetermined desired-level therein are then carriedpast thedragtool-1I3II andthis tends to. rotate the shaft I21'in'a clockwise direction and to pull the weight pan I31 upwardly through the system of lever arms and tie rod 'hereinabove described.

bowl I04," the greater -will be th drag on the drag tool I30=that tends-to-elevate the weight By placing weights on the weight pan I31'and while continuingtto rotatethe bowl I04, the device I can be brought into a state of equilibrium so that the end of-thearmI3I willberapstop screws 7 =I32I32,-and the-weight in: gramsrequired ton proximately midwaybetween achiev this condition of equilibriumpfor-qaparticular composition contained in the mixingbowl value isdependentmponthe dimensionsof the I 1 a aratus 1andsthevmannerofe i1s -o.f.@the rpar ri is the Wagner-Bowen plasticity value Carried bythe upper end of shaft'121 .and rotatable therewith is the arm I3I, the outer 1 I33 is fixedly carried by arm I06 and pivotally mounted thereon is the T-shaped scale beam member comprising the vertically-extending arm I34 and One end of the The greaterthe plasticity (i. e; theheavier the consistency) ofthe contents of-the p 2 inches tu's in makin-g the determination. The essential '1'--4 inches s1 A; inches :r% inch radius y-1l angle e--1 inch aa3%; inches bb2% inches g.-3% inches h2% inches .'.2% inches j-2 inches Ic-4% inch radius Z.-l%% inch radius cc% inch m- Q inch dd% inch n'2"/ inches ee-- inch jf-24 l5 angle gg inch radius q-Qfi inches hh inch The dimensions of the mixing blade H3 and of the smoothing blade H9 are indicated on the face of the drawings.

7 The Wagner-Bowen plasticity values at 400 F. given herein are determined in th following way. The height of the lower end of the measuring rod I24 from the bottom of the bowl I54 is adjusted so as to be inch. The height of the bottom of the drag tool E30 from the bottom of the bowl is set so as to be inch. The weight of the composition to be tested is approximately 1500 grams. The weight is not critical provided the thickness of the composition as it leaves the smoothing blade just clears the lower end of the measuring rod I24. The composition is mixed While in the bowl HM. Throughout the test the bowl E54 is rotated at the rate of 60 rotations per minute. The bitumen that is used in the com position while in a heat-liquefied condition is poured into the bowl While the bowl is rotating. The bitumen is'brought to a temperature of 400' F. by the burners and, while maintaining the temperature at 400 F., the filler material is added in small increments until it has all been incorporated. The smoothing blade H9 is then adjusted so that the composition as it leaves the smoothing blade just clears the lower end of the measuring rod I24. Weights are then placed on the weight pan i3! until the arm 13! is brought to a position between the stop screws I32, the weight to bring about this condition of equilibrium being recorded. Such recordings are made every five minutes until the recorded weight becomes constant for three consecutive readings. The weight in grams for the last three consecutive readings is taken as the Wagner- Bowen plasticity value of the composition at 400 F.

' In the formulation of highly fire-resistant o-1 inches bituminous coating compositions according to this invention, it is desirable that the Wagner- Bowen plasticity value not exceed about 1500 grams and it is preferable that this plasticity value not exceed about 1000 grams.

In addition to the fillers of the planar extended type that have been mentioned and illustrated by a number of examples hereinabove, other finelydivided filler materials may be employed. 'In the held of finely-divided solid water-insoluble heatresistant mineral fillers, such fillers may be exemplified by slate flour, limestone dust, silica flour, kaolinitic clay, hydrated Portland cement, talc, fly ash, dead burned calcium sulphate, precipitated calcium silicate hydrate and the like.

Inthe held of organic fillers of the finely divided solid water-insoluble type bituminous coal has been found by us to be particularly effective. Moreover, we have found that finelydivided bituminous coal, while not of the planarextended type, behaves similarly to the filler materials of the planar-extended type in that the coarser screen gradings have a greater stabilizing efiect upon the bitumen in bituminous compositions than the more finely-divided screen gradings. However, in the employment of bituminous coal it is essential that th bituminous coal be employed in a bituminous composition wherein there is a total filler content of at least 35% by weight of the bituminous, composition and wherein the total'filler content has a flow resistance coefficient of at least 75, and wherein the plasticity value as measured by the Wagner- Bowen plasticimeter -is not more than 1500 grams. If the bituminous composition is not thus formulated the coal and the asphalt flow and burn and little if any improvement in fire resist-' ance is afforded by the use of bituminous coal.

Since bituminous coal has the peculiar prop-- erty of behaving similarly to fillers of the planarextended type in that the different screen gradings differ considerably in their property of stabilizing the bitumen in bituminous compositions, we have assigned screen factors to the different screen gradings of bituminous coal in the same way that screen factors have been assigned to the different screen gradings of the fillers of the planar-extended type. Thus since a composition containing 45% by weight ofoxidized straight run asphalt having a softening point of about 230 F., 10% by Weight of slate flour about 85 of which is (200) and 45% by weight of a typical bituminous coal (such as Kentucky bituminous coal) of the screen grading (28+35) has a flow resistance coefiicient of about '75, it is seen that the'screen factor, of this screen grading of the bituminous coal is about 0.33. The screen factors of the other screen gradings of bituminous coal are determinable in a similar manner and are subject to considerable variation.

Other organic filler materials, while somewhat 7 less effective than bituminous coallikewise may either high temperature coking processes or by 7 low. temperature coking processes or such as socalled petroleum coke which is derived from petroleum. Coke is somewhat less ellective than bituminous coal, the screen factor of high temperature disintegrated coke of the screen grading (-28-l-35) being about .25.

Another organic filler which is similar to coal and coke in that, while not of the planar-extended type; the different screen gradings diiler in effectiveness (although not to the extent that different screen gradings of planar-extended fillers or coals and cokes differ in effectiveness) is finely-divided cork. Accordingly we have assigned to the different screen gradings of finely divided cork screen factors determined in the same way that the screen factors of the different screen gradings or" planar-extended filler materials are determined, By way of illustration the 25 screen factorbf thescreen grading f- '28-F'35Y'of cork isabout e. v

"In addition to foregoing, other finely-"divided solid water-insoluble 'organic fillers that" are not of the 'planar-extendedtype may be einployedin highly "fire resistant bituminous compositions according to this invention. "Examplesbf'suelforganic filler materials arethose "produced from hard rubber and from 'hardened resins suchas resins of the phenol-aldehyde type, Hgninresihs and the like. V

i In the case of organic filler "materialsitis desirable that the softening "point thereof as detera mined by the standard cube softening point test (carried out inair) -be at =-leasi /'-about500? and preferably be atieast abont 760 "ier-if the softening point issubstantiallylower, the filler will melt and blend with the waterproofingfbitumen when --thebituminous com pcsitien {is heat plasticized for -rnixing -=ai=id-' spreading. Finelydivided solid WELEGY-lilSOlllblB "mineral fi'llers having a softening point aboye500 F answererably above 700- likewisemay be employed.

An organic filler which has -a softening-point above about 500- F. but below about-1000- F: exercises a special efiect upon the-bituminous composition, for, when the bituminouscomposition is exposed to fiame-ternp'eratu-res, such-materials melt and blend with the Waterproofing bitumen (which-normally is re'ndered highly fiuidupon exposure to fiame temperatures) and converts the water-proofing bitumen tea more heavy and viscous massthat hasespeciallyhig-h resistance to flow.

Fillerswvhich are not of the planar-extended type can be employed by them'selves but in such case the criticalpoint atwhich high fiow resistance is is attained is-usually quite high and of-the order of 55-to 80%by weight of the bituminous compositions. Thus' the critical point for slate flour is-about-60 to'-65% by weight and is about '75 to 80% byweight in the case of-limestone dust. lFor kaolin clay, the critical-point is usually around 58% to" 68'% dependi-ng upontheparticu lar varietyof-claythat is employed. ln thecase of silica flour, the critical -point -isin the neighborhood of 70%. These data illustrate' the fact that, in the case ofeach filler rhateria-Ldricorporation' thereof in'a bituminouscomposition- -has'very little effect upon flow resistance or upo'n fire resistance up to a thecritical point, followed by sudden and very great 1 increase in flow resistance and fire resistance assoon as the critical point isreached.

-In the case of fillenmaterials such as slate flour, limestone dust, and the like, which are-not of the planar-extended typeitisprefei'able that atleast 9G.%-by weight pass a lUO meSh testing sieve. Referring tothe filler asawhole in the bituminous composition, including thepresence of planar extended filler, it is desirable that at least half by weightof the total filler pass a-lOO mesh testing sieve and preferable that at least /5; by weight of the total filler pass 'a 100 mesh testing' sieve. This is especially the case when the bituminous composition contains 55% by weight or more of filler. In the ordinary case, if the total filler is between 35% and 55%by'weight or even between 55% and 65% by weight of the bituminous composition, the major proportion of the' total fillerpasses a 100 meshtesting sieve and when the total filler is over-65% by Weight of the bituminous co'nipositionabout or more 'ofthe total filler passesa 100 meshteSting sieve. *In order to prevent the inclusion-anthe-bitminous the-organic fillers -justineirtion'ed. I r

-6ne reason Why -chrysotile asbestos"i eially 'dGSiiab1if01 employment in 'bit coating' e'oinpositi 'ns-i-n the practicefof th ventionis thatit contains about 12% (3045? by weightpf water ei cameramansteerablee or b81OW-fidfne temperature. Gariadjian and serpentine rec-l4 are similar to-chrys o t ile as-' bestos in this regard. Other materials such as kaolinit-ic clay, hydrated- Portland calcium silicate hydrate contain 10% y Weight of water of constitution. When the filler material in the bituminous composition-"centains water of constitution liberatable at orbelow name temperature, the liberation of moistiire causes the bituminous composition to develop pore to agreater extent than -otherwis'e when the ituminous composition is exposed tofiame temperature and this is desirable since the-pores tend to augment the heat-insulating. eiHCi'ency oxWhe mat-like residue-that results from exposure of the special bituminous"composition of this invention to flame temperature. It is 'desirable tiiat the bituminous composition have incorporated therein a filler containing Water of -constitution, which water of constitution liberatable atonbelowfiame temperature amounts to at least'fi 'by weight of thecoating-composition.

With regard to the waterproofing bitumen that employed in the speciaLfire-resistantbitumifiqil cqm qsiiiqmit s1usu 11yp e r e iii-the manufacture of sjhinglesprthe like to employ :an asphalt having a softening pointof about -200?F. 25? E? liq h aseme he broaderranse'is e m r as e t arsen s a in a so in preferable, even in the case of roll roofings and compositio'n. While the flow resist asphaltsas compared with "other asnaiwic preferable to use the typeoi 'rrfioiiii'gfasphalt where the roof ng is'to be erected directly to tha -sun and tow-earlier.

Where reference is made herein to tasi 27-= proofing bitumen, this term is used herein in reference to asphalt, pitch, tar and the like having a softening point below about 275 F. and unmixed with filler. One can employ as a finelydivi'ded solid water-insoluble organic filler, a bituininous material consisting wholly or partially of bitumen, said material having a softening point above 500 F., such as a pyrobitumen, e. g. grahamite, albertite and the like or even an asphalt which has been carried, as by air blowing, to a softening point above 500 F. Any such finelydivided bituminous material is to be regarded as organic filler rather than as part of the waterproofing bitumen in the bituminous composition. When reference is made herein to a bituminous material, or a bituminous composition, or a bituminous coating, or a bituminous layer, reference is made to a material, composition, coating or layer comprising bitumen either with or Without filler.

In the foregoing example of the practice of this invention, the special bituminous coating composition was applied in layer form at the rate of 45 pounds per 100 square feet of the roofing. It is usually desirable to apply the special bituminous coating material to the weather-exposed side of the base sheet so that the layer will weigh at least 20 pounds per 100 square feet, the range ordinarily being from about 20 to about 60 pounds per 100 square feet, although about 30 to about 50 pounds per 100 square feet is usually preferable. In the foregoing example, wherein the special bituminous coating material contained substantially 50% by weight of filler and the coatingwas applied at the rate of 45 pounds per 100 square feet, the amount of filler in the coating composition constituted about 22.5 pounds per 100 square feet of the roofing material. For prepared roofing materials, it is usually desirable that the roofing material contain in one or more layers, such as a surface layer or backing layer, sufficient of the special bituminous composition so that the roofing material will contain at least 7 and preferably at least'about-14 pounds per 100 square feet of the filler material. By varying the number and thickness of the layers of special bituminous coating composition of this invention, varying degrees of fireretardant effectiveness can be attained. 'The special bituminous composition of this invention is especially effective when it is dispersed in a roofing so as to occur in a plurality'of layers rep resented by felt or other sheet material, for example, as shown in Figs.- 6 and 9. In such plural layer construction, it is desirable that the total filler constitute at least about pounds per 100 square feet of the roof covering and prefere ably about 42 pounds per 100 square feet of the roof covering. It is also desirable that each of at least two layers of the special bituminous composition contain at least 7 pounds per 100 square feet and preferably at least about 14 pounds per 100 square feet of the roof covering of the finely-divided solid water-insoluble heatresistant mineral filler.

While embodiments of this invention have been shown in the form of preformed roofing materials such as shingles and roll roofing, it is apparent that the special bituminous composition of this invention may be employed in the manufacture of roof coverings installed on the job, such as built-up roofings, certain types of which are exemplified in our aforesaid application Serial Numiber 370,636.

tria e? It is one of the advantages of this invention that the new roofing herein defined possess high fire resistance without sacrifice of other properties required for a roofing and without substan-v tial increase in cost compared with conventional roofings heretofore manufactured. V roofing of this invention has very good weathering characteristics and is tough and pliable. Thus a typical preformed roofing material such as a shingle can be bent'l80" in two seconds around a 4 centimeter mandrel with the fire-resistant special coating composition on the outside without cracking the coating through to the felt base, the test being made at 77 F. Itis desirable that a roofing having a bituminous waterproofing coating be suficiently pliable to be bent 180 in two seconds about amandrel l0 centimeters in diameter at 77 F. with the coating on the outside without cracking the coating through to the base on which it is applied, and any such coating or layer is referred to herein as pliable at ordinary temperatures.

While felt sheet material has been mentioned hereinabove as the strain-resisting sheet-like element of roofings and roof coverings embodying this invention, it is apparent that any other suitable sheet material, either fibrous or nonfibrous, either foraminous or non-foraminous, and either deformed or non-deformed, that is adapted to afford the desired strength characteristics, may be employed. Thus fabrics other than felt may be employed such as woven fabrics or fabrics of unspun bonded fibers. The base sheet may, if desired, be saturated with a bituminous or other waterproofing material or may be dry. Sheet material such as a composition board or insulation material may be employed.

' Plain or corrugated or indented sheet metal may be employed as the base'sheet. Ordinary roofing felt made of organic fibers is, however, the most inexpensive sheet material, and, notwithstanding the combustibility of such sheet material, roofings comprising it can, according to this invention, be made highly fire-resistant. If desired, non-combustible fibers can be incorporated in the felt or other fibrous base sheet to augment the fire resistance of the roofing.

It is apparent from the foregoing that, according to the present invention, organic filler materials which need not be non-combustible, when incorporated in bituminous coating compositions within the critical limits above defined, have the astonishing efiect of greatly increasing the flow and fire resistance of bituminous roofings. Use of such organic filler materials isof particular utility in imparting to a bituminous composi tion a fiow resistance coefficient over (and preferably over where the heat-resistant mineral filler in the, composition is present in an amount below the critical amount for attaining high flow resistance and high fire re-. sistance. Moreover, bituminous compositions, wherein the heat-resistant mineral filler in itselfhas high flow resistance, can be further improved both as to flow resistance and as to fire resistance by the incorporation of organic filler as disclosed and claimed herein.

While this invention has been described in connection with certain typical examples of the practice thereof, it is to be understood that this has been done for purposes of exemplification. Accordingly the scope of this invention is to be governed by the-language of the following claims construed in the light of the foregoing description of our invention.

The newvwecla m 1. A roofing having high resistance to fire,

.cpmprising, ,sheet like H base materia1...and carried by said sheet like base materiaLalayer of. thermoplasticbituminous composition, said bituminouscomposit-ion containing waterproofing biltumen having a softening point above 30 F. and ;not j;above ;275 Fqand of, the. range 20% to 65% by; weight of, said/composition, and said composition. containing intimately commingled and distributed. uniformly throughout finely-divided solid ,waterginsoluble filler of: the range 35% to 80% .byvweight of said composition and having a softeningrpoint above 500. Fz said filler consist- .ing ofa mixture of organic filler and heat-resistant mineral filler, and said filler having a flowgresistance coefiicient of at least "(5 when said compositioncarriedbysaid sheet-like base material is exposed to flame temperature under the flow resistance-test defined herein, said heatresistant mineral filler with-out said organic; filler having a flow resistance coefficient lessgthan [(5, said bituminous, compositionv having, a Wagner- Bowen plasticity value at'400 P. not substantiallyigreater than 1500 grams, and said bituminous composition providing apliable weather resistant llayer of the-hot-spread coating type in- ;tegrally bonded with said-sheet-like base material.

:.2. A- roofinghaving highfire resistance, oomprising-sheet-likebase material and carried by said sheet-like base-material alayer of thermoplastic bituminous composition, said bituminous. composition containing waterproofing bi- :tumen having a softening point above 80 F. and notlabove 275F and ofthe range 20% to 65% by weight of said bituminous composition, and said bituminous composition containing intimately commingled and distributed uniformly throughout finely-divided solid water-insoluble filler having a softening point above 500 F. and of the range 35% to 80% by weight of said composition, said iiller comprising heat resistant mineral filler the ratio of the percent by weight of which to the percent by weight of the waterproofing bitumen in said bituminous composition is at least 1 to 3 and comprising organic filler, the total in said composition consisting in major proportion by weight of particles passing a 100 mesh testing sieve and having a flow-resistance coeflicient of at least 75 when said hituminous composition carried by said sheet-like base material is exposed to flame temperature under the flow-resistance test as defined herein, but said heat-resistant mineral filler without said organic filler having a flow-resistance coefiicient less than 75, said bituminous composition having a Wagner-Bowen plasticity value at 400 F. not substantially greater than 1500 grams, and said bituminous composition providing a pliable Weather resistant layer of the hotspread coating type integrally bonded with said sheet'like base material.

3. A roofing, according to claim 2, wherein said finely-divided solid water-insoluble filler comprises filler which is selected from the group consisting of planar-extended filler that passes a 6 mesh testing sieve and that does not have more than one dimension greater than .046 inch, coal passing a 14 mesh testing sieve, coke passing a 14 mesh testing sieve, and cork passing a 14 mesh testing sieve and the ratio of the grading index of which to the percent by weight of bitumen in said bituminous composition is at least 1 to 3 and not greater than 1 to 0.7, and wherein the 530 said.- organic filler in. said composition is essential to; said minimum ratio.

s14. A: roofing having high resistance to fire, comprisingisheet like base material and carried ,bysaidsheet-like base material a layer of thermoplastic bituminous composition, said bituminous composition containin waterproofing' bitumen having a softening point above 'Fl and snot above' 2fZ5 -F. and of the range'20% to 65% rbyiweight of said composition, andsaid composition :containing intimately commingled and distributed. uniformly throughout finely-divided solid ;water.-.insoluble filler having a softening point-above500 F. andof the range 35% to 80% :byiweight of .said bituminous. composition, said dilleraconsisting of a mixture of heat-resistant imineralifillerl and coal, said filler having a flowresistanceacoefficient of at least 75 when said -bixtum-inousecomposition isexposed to flame temperature .undertthe flow-resistance test defined herein,:saidheat-resistant mineral filler withoutlsaidcoalhavingea flow resistance coeflicient less than '75,.said bituminous composition having ,aiWagnerp-Bowen plasticity valueat 400 F. not greater than about 1500 grams, and said bituminouscomposition providing a pliable weather resistantlayenof the hot-spread coating type integrallyibonded with said sheet-like base material.

j; 5. 33A; roofing, according to claim-4, wherein said heatrresistant mineralfiller comprises asbestiorm mineral fiber.

6. .1 1 roofing having high resistance to fire, accordingto claim: 1, wherein said sheet-like base material is fibrous .sheet material and wherein the flow: resistance. coefficient of .said finelydivided solid water-insoluble filler having a softening point above 500 F. is at least 90.

7. A highly fire-resistant prepared bituminous roofing material according to claim 1, wherein said sheet-like base material consists essentially of felted fiber sheet material impregnated with a bituminous Waterproofing material, wherein said thermoplastic bituminous composition is applied to said sheet-like base at the rate of about 20 to 60 pounds per square feet of said roofing and wherein granular surfacing material is embedded in the. normally weather exposed surface of said layer of thermoplastic bituminous composition that is integrally bonded with said sheet-like base material.

8. A roofing according to claim 1 wherein said filler comprises planar-extended filler which passes a 6 mesh testing sieve and which has not more than one dimension greater than .046 inch, the ratio of the grading index of said planarextended filler to the percent by weight of bitumen in said bituminous composition being at least 1 to 3 and not being substantially greater than 1 to .7.

9. A prepared roofing material having high resistance to fire according to claim 1 wherein the softening point of said waterproofing bitumen is of the range F. to 275 F. and wherein said bituminous composition is applied at the rate of about 20 to 60 pounds per 100 square feet of said roofing material to provide said pliable weather resistant layer of the hot spread coating type integrally bonded with said sheet-like base material.

10. A roofing having high resistance to fire according to claim 1 wherein a major proportion by weight of said finely-divided solid water-insoluble filler consists of particles passing a 100 mesh testing sieve, wherein there is a plurality 

1. A ROOFING HAVING HIGH RESISTANCE TO FIRE, COMPRISING SHEET-LIKE BASE MATERIAL AND CARRIED BY SAID SHEET-LIKE BASE MATERIAL A LAYER OF THERMOPLASTIC BITUMINOUS COMPOSITION, SAID BITUMINOUS COMPOSITION CONTAINING WATERPROOFING BITUMEN HAVING A SOFTENING POINT ABOVE 80* F. AND NOT ABOVE 275* F, AND OF THE RANGE 20% TO 65% BY WEIGHT OF SAID COMPOSITION, AND SAID COMPOSITION CONTAINING INTIMATELY COMMINGLED AND DISTRIBUTED UNIFORMILY THROUGHOUT FINELY-DIVIDED SOLID WATER-INSOLUBLE FILLER OF THE RANGE 35% TO 80% BY WEIGHT OF SAOD COMPOSITION AND HAVING A SOFENTING POINT ABOVE 500* F., SAID FILLER CONSISTING OF A MIXTURE OF ORGANIC FILLER AND HEAT-RESISTING MINERAL FILLER, AND SAID FILLER HAVING A FLOW RESISTANCE COEFFICIENT OF AT LEAST 75 WHEN SAID COMPOSITION CARRIED BY SAID SHEET-LIKE BASE MATERIAL IS EXPOSED TO FLAME TEMPERATURE UNDER THE FLOW RESISTANCE TEST DEFINED HEREIN, SAID HEATRESISTANT MINERAL FILLER WITHOUT SAID ORGANIC FILLER HAVING A FLOW RESISTANCE COEFFICIENT LESS THAN 75, SAID BITUMINOUS COMPOSITION HAVING A WAGNERBOWEN PLASTICITY VALUE AT 400* F. NOT SUBSTANTIALLY GREATER THAN 1500 GRAMS, AND SAID BITUMINOUS COMPOSTION PROVIDING A PLIABLE WEATHER RESISTANT LAYER OF THE HOT-SPREAD COATING TYPE INTEGRALLY BONDED WITH SAID SHEET-LIKE BASE MATERIAL. 